Lighting systems have traditionally involved the use of incandescent or fluorescent lighting. Recent advances in the use of light emitting diodes has, however, resulted in greater use of LEDs for not only display and accent lighting but interior lighting as well. With the use of LEDs comes the problem of how to disperse the concentrated light ray of the LED so as to create a more uniform and comfortable lighting environment. In addition to developing ways to disperse the LED lighting, there is also a need to improve lighting systems for use with a dropped ceiling in order to meet regulatory restrictions that deal with dropped-ceiling mounted luminaires.
Some of the more difficult regulatory restrictions to deal with involve the fact that the entire barrier between plenum space and occupied space must be bounded by an approved structural and fire rated material. Additionally, the system must be strong enough to support a load greater than its own weight, and must be anchored against earthquake, physical strikes and vibration. Furthermore, any potentially dangerous electrical components, including LED power sources must be isolated from any interaction with nearby materials or occupants. Finally, the amount of light, and the distribution of light into the occupied space is fairly static and defined by the space to be lit. Therefore, any reduction in the size of the luminous source will result in a brighter and higher glare appearance. The entire ceiling grid area, however, must glow uniformly in order to create the highest visual comfort. Finally, the luminous appearance of the energized lighting system must be visually comfortable. Also, the luminous area of the lighting system must be made as large as possible to reduce its contrast with the surrounding ceiling tiles.
Previous lighting systems for use with a dropped ceiling have involved the use of fluorescent lighting. For example, U.S. Pat. No. 5,777,857 (Degelmann) is directed to an energy efficient lighting system for use with T8 fluorescent tubes. Given the regulatory restrictions and the need to create a comfortable lighting environment using LEDs, a dropped-ceiling lighting system that would satisfy the regulatory requirements and provide for uniform lighting would be an important improvement in the art.